In the study of ion implantation, electrically active ionsornoble gas ions are often used for damage study, range profiling, etc. Very seldom are both electrically active ionsandnoble gas ions implanted at about the same depth. In the work reported here, argon and arsenic ion implants and their interference in diffusion were studied by using backscattering, electrical measurements, and transmission electron microscopy (TEM). Several unexpected phenomena were observed.